The statements in this section merely provide background information related to the present disclosure. Accordingly, such statements are not intended to constitute an admission of prior art.
Powertrain systems may be configured to transfer torque originating from multiple torque actuators through a torque transmission device to an output member that can be coupled to a driveline. Such powertrain systems include hybrid powertrain systems and extended-range electric vehicle systems. Control systems for operating such powertrain systems operate the torque actuators and apply torque transfer elements in the transmission to transfer torque in response to operator-commanded output torque requests, taking into account fuel economy, emissions, driveability, and other factors. Exemplary torque actuators include internal combustion engines and non-combustion torque machines. The non-combustion torque machines may include electric machines that are operative as motors or generators to generate a torque input to the transmission independently of a torque input from the internal combustion engine. The torque machines may transform vehicle kinetic energy transferred through the vehicle driveline to electrical energy that is storable in an electrical energy storage device in what is referred to as a regenerative operation. A control system monitors various inputs from the vehicle and the operator and provides operational control of the hybrid powertrain, including controlling transmission operating range and gear shifting, controlling the torque actuators, and regulating the electrical power interchange among the electrical energy storage device and the torque actuators to manage outputs of the transmission, including torque and rotational speed.
Known multi-mode electrically-variable transmissions (EVTs) can be configured to operate in one or more fixed-gear ranges, one or more electric vehicle (EV) ranges and one or more electrically-variable transmission (EVT) ranges. Known shifts between first and second EVT ranges occur at a synchronous speed point. Known shifts are executed by using one of the EVT ranges to slew engine speed to a desired transmission ratio to effect a shift including synchronous activation of an oncoming clutch. Transmission output torque may be well controlled during this type of shift, but the shift time can be long and require engine speed changes that can be noticeable to a vehicle operator. Furthermore, it may be desirable to shift between two EVT modes while maintaining a constant engine speed in order to provide a vehicle feel that is perceived as smooth by the operator. For example, during a transition from an EV drive mode to an engine-on operation at moderate to high vehicle speeds, the engine start occurs in a first, lower EVT range, e.g., an input-split range, with the transmission immediately transitioning to a second higher EVT range having a compound-split range to effect more efficient operation at higher vehicle speed. Required maximum torque from a first torque machine can be defined at a synchronous point for a transition from an input-split range to a compound-split range since the first torque machine must react torque from the engine and torque from a second torque machine in the compound-split arrangement.